Interleukin-1 ("IL-1") is a major pro-inflammatory and immunoregulatory protein that stimulates fibroblast differentiation and proliferation, the production of prostaglandins, collagenase and phospholipase by synovial cells and chondrocytes, basophil and eosinophil degranulation and neutrophil activation. Oppenheim, J. H. et al, Immunology Today, 7, pp. 45-56 (1986). As such, it is involved in the pathogenesis of chronic and acute inflammatory and autoimmune diseases. IL-1 is predominantly produced by peripheral blood monocytes and exists in two distinct agonist forms, IL-1.alpha. and IL-1.beta.. Mosely, B. S. et al., Proc. Nat. Acad. Sci., 84, pp. 4572-4576 (1987); Lonnemann G. et al., Eur.J. Immunol., 19, pp. 1531-1536 (1989).
IL-1.beta. is synthesized as a biologically inactive precursor, pIL-1.beta.. pIL-1.beta. is a 33 kDa polypeptide that lacks a conventional leader sequence and is not processed by a signal peptidase. March, C. J., Nature, 315, pp. 641-647 (1985). Instead, pIL-1.beta. is cleaved by interleukin-1.beta. converting enzyme ("ICE") between Asp 116 and Ala 117 to produce the biologically active C-terminal fragment of 17 kDa molecular weight found in serum and synovial fluid. Sleath, P. R. et al., J. Biol. Chem., 265, pp. 14526-14528 (1992); Howard, A. D. et al., J. Immunol., 147, pp. 2964-2969 (1991). Processing by ICE is also necessary for the transport of mature IL-1.beta. through the cell membrane.
ICE is a cysteine protease localized primarily in monocytes. It converts precursor IL-1.beta. to the mature form. Black, R. A. et al., FEBS Lett., 247, pp. 386-390 (1989); Kostura, M. J. et al., Proc. Natl. Acad. Sci. USA, 86, pp. 5227-5231 (1989). ICE, or its homologues, also appears to be involved in the regulation of cell death or apoptosis. Yuan, J. et al., Cell, 75, pp. 641-652 (1993); Miura, M. et al., Cell, 75, pp. 653-660 (1993); Nett-Fiordalisi, M. A. et al., J. Cell Biochem., 17B, p. 117 (1993). In particular, ICE or ICE homologues are thought to be associated with the regulation of apoptosis in neurogenerative diseases, such as Alzheimer's and Parkinson's disease. Marx, J. and M. Baringa, Science, 259, pp. 760-762 (1993); Gagliardini, V. et al., Science, 263, pp. 826-828 (1994).
ICE has been previously described as a heterodimer composed of two subunits, p20 and p10 (20 kDa and 10 kDa molecular weight, respectively). These subunits are derived from a 45 kDa proenzyme (p45) by way of a p30 form, through an activation mechanism that is autocatalytic. Thornberry, N. A. et al., Nature, 356, pp. 768-774 (1992). The ICE proenzyme has been divided into several functional domains: a prodomain (p14), a p22/20 subunit, a polypeptide linker and a p10 subunit. Thornberry et al., supra; Casano et al., Genomics, 20, pp. 474-481 (1994).
Full length p45 has been characterized by its cDNA and amino acid sequences. PCT patent applications WO 91/15577 and WO 94/00154. The p20 and p10 cDNA and amino acid sequences are also known. Thornberry et al., supra. Murine and rat ICE have also been sequenced and cloned. They have high amino acid and nucleic acid sequence homology to human ICE. Miller, D. K. et al., Ann. N.Y. Acad. Sci., 696, pp. 133-148 (1993); Molineaux, S. M. et al., Proc. Nat. Acad. Sci., 90, pp. 1809-1813 (1993). Knowledge of the primary structure of ICE, however, does not allow prediction of its tertiary structure. Nor does it afford an understanding of the structural, conformational and chemical interactions of ICE and its substrate pIL-1.beta. or other substrates or inhibitors.
ICE inhibitors represent a class of compounds useful for the control of inflammation or apoptosis or both. Peptide and peptidyl inhibitors of ICE have been described. PCT patent applications WO 91/15577; WO 93/05071; WO 93/09135; WO 93/14777 and WO 93/16710; and European patent application 0 547 699. However, due to their peptidic nature, such inhibitors are typically characterized by undesirable pharmacologic properties, such as poor oral absorption, poor stability and rapid metabolism. Plattner, J. J. and D. W. Norbeck, in Drug Discovery Technologies, C. R. Clark and W. H. Moos, Eds. (Ellis Horwood, Chichester, England, 1990), pp. 92-126. This has hampered their development into effective drugs.